A heat pipe is a device that has an extremely high thermal conductivity and that is used to transport heat. In order to achieve this, heat pipes take advantage of simple physical effects:
As a liquid evaporates, energy—in the form of heat—must be taken from the environment. Therefore, an evaporating liquid will cool the surrounding area. This is how a heat pipe effectively cools the heat source. However, this doesn't get rid of the heat; heat is just transported with the vapor. At the target side for heat transport, the heat pipe must be cooled, for example using a heat sink. Here, the inverse effect takes place: the liquid condenses and, therefore, emits heat. Using these effects, it is possible to build heat pipes that have a thermal conductivity that is many thousand times higher than a copper piece of the same size.
FIG. 11 (prior art) is a schematic view of a heat pipe 10. Referring to FIG. 11, the heat pipe 10 includes a closed metal tube 12 filled an amount of working fluid 18a, 18b. The heat pipe 10 further includes a heat sink 14 mounted on an upper side of the closed metal tube 12. If a heat source 16 is applied to the lower side, the working fluid 18a will evaporate, while cooling the heat source 16. The working fluid 18a will move up and condense near the heat sink 14 on top. From there, the working fluid 18b will drip back to the heat source 16. Such working fluid 18b drips with the help of gravity, so this heat pipe 10 works in only vertical orientation.
What is needed, therefore, is a heat pipe which may not rely on gravity alone to move a working fluid to a heat source.